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Published: Wednesday 31 July, 2013

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The observations support larger estimates of how much methane is stored under the worlds oceans and could be used to monitor areas where methane might be released in large bursts. Such measures are important given that some scientists have concerns about catastrophic releases of methane contributing to climate change, and others are keen on mining such deposits for fuel.



Researchers have known since the 1960s that there are some natural deposits of frozen ice containing methane lying on the ocean floor, where the high pressure and cold temperature keep them from melting. Oceanographers have pulled up frozen chunks of this material, called methane clathrate or hydrate, from more than 90 locations around the world and have estimated from acoustic studies and assumptions about where hydrate might reasonably form that there is some 10,000 gigatonnes of carbon stored in this way under the sea. Thats twice as much as the carbon thought to be in conventional fossil fuels. Some have speculated that sudden melting of subsea hydrates, thanks to a warming ocean for example, released massive amounts of methane into the atmosphere and triggered rapid climate change in the past.



But current estimates of the amount of methane buried under the sea are missing a big part of the picture, says Peter Brewer, ocean chemist at the Monterey Bay Aquarium Research Institute in Moss Landing, California. In addition to the natural gas stored inside the ice, he says, there must be a lot of gas in the water saturating the mud in which that ice is buried. Otherwise, he cheap bags for sale online says, the hydrate wouldnt be stable. If you just put a block of methane hydrate on the sea floor it will dissolve really fast, he says. The hydrates in sediments have to be in equilibrium with the water arou cheap bags for sale online nd them, which must contain huge amounts of methane. The robotic sub can stick its metal probe into the mud next to a hydrate deposit and suck up water, and then a laser beam reveals the amount of methane and other cheap bags for sale online substances in that water all without leaving the sea floor. Previous studies have tried to pull up mud to the surface for analysis, but the change in pressure means that most of the gas escapes along the way. Onsite measurements were long thought to be impossible because of interfering fluorescence problems, but Brewers team has shown it can be done.



The champagne of greenhouse gases For their paper in Geophysical Research Letters1, they visited three sites Barkley Canyon offshore British Columbia, Hydrate Ridge offshore Oregon and an area offshore Los Angeles and found high concentrations of methane, at pressures up to three times that in a champagne bottle, corked up in the mud.



The technique, says Brewer, could be used to check up on areas where it is suspected that a large volume of gas might be set to be released. If you see bubbles of methane coming out of the water or the sea floor, is that an isolated chimney of gas or is it a large area poised for release? There has been no way of knowing. Now you can go measure it, he says. Its a really powerful tool.



Its expensive, but its useful, says Ross Chapman, a geophysicist at the University of British Columbia who studies hydrates and was not involved with Brewers work. Its nice to see these results, he says, even if they simply confirm what everyone suspected: theres a lot more methane down there than is apparent from cores brought up to the surface.



All this said, both Chapman and Brewer think that mass releases of seafloor methane are unlikely to cause a blip in todays climate, as released gas is more likely to get chewed up by bacteria or dissolved into the sea water rather than released to the air. Its not a scare story, says Brewer. Its hard to imagine this happening, agrees Chapman. Warming happens at the surface, and that would have to work its way down to the bottom.



G. Thomas: The Arctic Methane is already being released. This is due primarily due to warming since the last ice age, the resultant sealevel rise, and inundation by relatively warm water of areas that had prior been in a subaerial permafrost conditions This ice stored organic material, which is now thawing and rotting. The link to hydrate of this stink is tenuous at best, and not necessary as there are plenty of sources for methane up there now and the shallow water and onland permafrosts hydrates are too deeply buried anyway.



Not sure how you determine it is the greatest threat. A major asteroid collision would be bad too, and probably as likely as all the hydrates somehow melting all at once. cheap bags for sale online

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